Joule Thief 101

[EMJunkie]

Chris:

You are just "injecting noise" into the discussion and your posting should be completely ignored.  PW is dead-on 100% correct and Brad should undertake to learn and understand this fundamental concept.

MileHigh

The only Noise around here is you MileHigh - Looks like you can not read as well?

Most everyone here has learnt fo filter your non-sense out however. Its a new type of filter, called a MilleHehehehe Filter!

   Chris Sykes
       hyiq.org

[picowatt]

Just a bit more on the subject:

Let's say we build a very narrow bandpass filter circuit that only passes 900Hz with very steep rejection of frequencies that are above or below that 900Hz.  Using our function generator (FG), we input a 100Hz sine wave to that filter and note that there is little if any signal passing thru to the output (it is, afterall, a very narrow 900Hz bandpass filter).

Without changing the frequency setting on the FG, we switch to a triangle wave like in EMJ's post above (still at 100Hz).  Now when we look at the filter's output, we see a significant amount of signal passing thru the narrow 900Hz bandpass filter.

How can that be, the FG (and the scope) continue to say 100Hz?  The answer is that we have changed the frequency content of the waveform by adding a bunch of odd harmonics, just as is indicated by the frequency domain display EMJ posted above.

These are very real harmonics, not just abstract concepts or "noise"...

PW

[EMJunkie]

Tinman was not correct...

His LED was being driven by the higher frequencies contained in his waveform well in excess of the 10KHz indicated on his scope.   

A pure "sine wave" contains no harmonics.  If it contains harmonics (as in distortion, THD, etc) then it is no longer just a sine wave and its shape will deviate (distort) from that of a pure sine.

A triangle wave, like a square wave, contains ODD harmonics, just as is indicated by the frequency domain plot EMJ posted (note there are no even harmonics displayed).  The difference being that the amplitude of the higher frequency harmonics are rolled off in the triangle wave.

PW

PW - Thanks for correcting me!

...sine waves are representations of a single frequency with no harmonics

I must have had the Triangle and Square mixed with the Square and Sine.


Like you say, Sine waves do have Harmonics, but result in a distortion:


   Chris Sykes
       hyiq.org

[MileHigh]

Like you say, Sine waves do have Harmonics, but result in a distortion:

No, read PW's posting again.  Sine waves do not have harmonics.  A slightly distorted sine wave is by definition a fundamental sine wave plus some added harmonics.

You can go from the time domain to the frequency domain and then back to the time domain.  It's a very important concept.  I am pretty sure that's how they developed the algorithm for mp3 audio compression.  They take the audio time domain waveform and convert it into the frequency domain.  This is a much more efficient way of representing a waveform.  Then they compress the data associated with the frequency domain to give you a very efficient compression scheme.  Then when an mp3 is played back, the reverse is done.  The compressed frequency domain information is decompressed and then converted back to the time domain.

It's also the basis for a lot of image compression algorithms also.  That's why sometimes in a heavily compressed image you see "ripples" around small objects that are high-contrast relative to the background.  The "ripples" are waves - compression artifacts from a heavily compressed image where the compression algorithm primarily operates in the frequency domain.

[EMJunkie]

No, read PW's posting again, sine waves do not have harmonics.  A slightly distorted sine wave is by definition a fundamental sine wave plus some added harmonics.

Millehehehehe - Old Mate...

I think Reading is not one of your strong points? I quote again:

A pure "sine wave" contains no harmonics.  If it contains harmonics (as in distortion, THD, etc) then it is no longer just a sine wave and its shape will deviate (distort) from that of a pure sine.

I really dont see this as hard to understand, it is certianly not any deviation from what I have already said in my posts and already clearly quoted!!!


   Chris Sykes
       hyiq.org